Substrate fabrication

ABSTRACT

Systems and methods for fabricating bodies (e.g., porous bodies) are described. Various aspects provide for reactors and the fabrication of reactors. Some reactors include surfaces that provide for heterogeneous reactions involving a fluid (and/or components thereof). A fluid may be a gas and/or a liquid. A contaminant in the fluid (e.g., a dissolved or suspended substance) may react in a reaction. A contaminant may be filtered from a fluid. Some reactors provide for independent control of heat transfer (between the fluid, the reactor, and the environment) with respect to mass transfer (e.g., fluid flow through the reactor).

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division and claims the priority benefit of U.S.patent application Ser. No. 12/756,987, filed Apr. 8, 2010 now U.S. Pat.No. 8,277,742, which claims the priority benefit of U.S. provisionalpatent application No. 61/167,857, filed Apr. 8, 2009, the disclosuresof which are incorporated herein by reference. This description isrelated to U.S. patent application Ser. No. 12/183,917, filed Jul. 31,2008, the disclosure of which is incorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention relates generally to reactors, and moreparticularly to fabricating substrates that may be used in reactors.

2. Description of Related Art

Many reactions involving fluids (e.g., gases, liquids, and the like) usereactors. Many reactions are temperature dependent, and so a reactor (orzone within a reactor) may be required to have certain chemical,mechanical, thermal, and other properties at a temperature of interestto the reaction. Some reactions are performed at high temperatures(e.g., above 100 C., above 400 C., above 800 C., above 1100 C., or evenabove 1500 C.), and so may require reactors having appropriateproperties at the temperature of interest. Some reactions entail aheterogeneous reaction (e.g., involving a fluid and a surface).

Abatement of exhaust streams (e.g., from engines, turbines, powerplants, refineries, chemical reactions, solar panel manufacturing,electronics fabrication, and the like) may include heterogeneousreactions. In some cases, the period of time during which a fluidinteracts with a surface may affect the efficacy of a reaction. Certainreactions may benefit from increased contact times between a fluid and asubstrate. Certain reactions may benefit from reduced contact timesbetween a fluid and a substrate.

Some reactions proceed at practical rates at high temperatures. In somecases, an exhaust stream may provide heat that may heat a reactor (e.g.,as in a catalytic converter on an automobile). Controlling both contacttime (e.g., between a fluid and a reactor) and a temperature at whichthe reaction occurs may be challenging with typical reactor designs,particularly when heat transfer and mass transfer are not independentlycontrolled.

Effective reaction (e.g., mitigation of a pollutant) may require areactor design that maintains a desired temperature or range oftemperatures over a certain volume or region having a certain surfacearea, notwithstanding that the primary source of heat to the reactor maybe the exhaust stream. Such requirements may be challenging,particularly when mass transfer and/or reaction kinetics are at oddswith heat transfer kinetics (e.g., from an exhaust stream to a reactor,or from the reactor to the environment).

The use of exhaust heat to maintain a reactor temperature may result inimpaired performance under some conditions. For example, a catalyticconverter may inefficiently decompose pollutants prior to having beenheated to an appropriate temperature (e.g., when the vehicle is cold). Adiesel particulate filter may require “regeneration” (e.g., the creationof a temperature and oxygen partial pressure sufficient to oxidizedaccumulated soot). Regeneration often requires heating the filtered sootto an oxidation temperature, which often relies on heat from the exhauststream and/or heat from other sources. Regeneration may requireelectrical heating of a reactor. Some combinations of engines and dutycycles may result in contaminants (e.g., soot) reaching unacceptablelevels before a mitigation system begins efficient operation (e.g., asoot filter may “fill up” before regeneration occurs.

Regeneration may require injection of a fuel and associated combustionheating beyond the motive heat associated with the working engine (e.g.,direct injection of fuel into an exhaust stream). In some cases, theprovision of regeneration heat (e.g., via electrical heating,post-injection, downstream injection, and the like) may decrease theoverall efficiency of a system.

Some streams of fluids may be subject to a plurality of reactions and/orreactors. For example, a diesel exhaust mitigation system may include adiesel oxidation reactor (e.g., to oxidize CO and/or hydrocarbons), aparticulate filter, and a reactor to remove NOx (oxides of Nitrogen). Insome cases, these reactors are disposed in series, and so an exhaustsystem may include several components, each having an inlet and outlet,with the outlet of one component connected to the inlet of anothercomponent. Such systems may be complex and/or difficult to integrate.

In some cases, each component may require a separate mass and/or heatinjection apparatus. For example, excess diesel fuel may be injectedinto an exhaust stream to create combustion at a diesel oxidationreactor in order to raise an inlet temperature of a particulate filter.A NOx reactor may require injection of a reductant, (e.g., urea,ammonia, Hydrogen, and/or other fuel) in order to facilitate a reactionat a certain temperature. A diesel particulate filter may benefit fromNOx injection (e.g., to oxidize soot).

In some cases, latent heat and/or chemical species exiting a firstreactor may not be efficiently utilized in a second “downstream”reactor, notwithstanding that the heat and/or species might be useful inthe downstream reactor. In some cases, the heat and/or species exiting afirst reactor must be controlled in such a way that performance of adownstream reactor is not inhibited. Improved reactor designs mightprovide for such control.

Many refractory substrates (e.g., catalytic converter, dieselparticulate filter, and the like) are fabricated using extrusion. Suchsubstrates often have long channels, with the “long” direction of thechannels associated with the extrusion direction. The long direction mayalso be aligned with the flow of fluid through the substrate. As aresult, reaction kinetics, heat transfer kinetics, fluid flowproperties, and the like may be constrained by the method of fabricationof the substrate (e.g., extrusion). For example, a certain minimumresidence time (associated with a reaction) may require a substratehaving a minimum length, which may dictate an extruded substrate whoselength is impractical for a given application.

For a typical filter (e.g., a diesel particulate filter, or DPF),filtration may preferentially begin at regions having higher fluid flowrates. In some cases, the deposition of particles may preferentiallyoccur at the downstream end of a filter substrate, and so a particulatefilter may “fill up” from the downstream end toward the upstream end.

A DPF may be “regenerated” by oxidizing filtered particles (e.g.,filtered soot). Often, the downstream end of a DPF substrate may becooler than the upstream end, and so regeneration of soot may requirethat the coolest part of the substrate reach regeneration temperatures.In certain applications, it may be advantageous to provide forpreferential soot filtration at portions of the substrate that heat upfaster than other portions.

SUMMARY OF THE INVENTION

Reactors and reactor substrates are described. Design guidelines aredescribed. In some embodiments, a reactor design provides for improvedcontrol of heat transfer between a fluid and a reactor involved in areaction with the fluid. Certain reactors may be used for filtration ofparticulates from a fluid stream. In some cases, preferential filtrationmay occur in regions of a reactor that are more amenable toregeneration. In some cases, soot may preferentially be filtered inregions of a reactor that reach regeneration temperatures sooner thanother regions of the reactor.

Methods for forming reactors are described. Certain methods includedepositing a layer of particulate material and bonding a portion of thelayer using a bonding apparatus. Bonding may include incorporating apolymer into the layer, and in some cases, a laser may be used to fusethe portion. A layer may include a first material (e.g., a ceramicpowder from which a reactor may be fabricated) and a second material(e.g., a binder to bind the powder). A layer may include a fugitivephase. A binder may behave as a fugitive phase. An activator may bedeposited onto portions of the layer, which may activate bonding amongthe various particles exposed to the activator. A binder may includeorganic material (e.g., a polymer), which in some embodiments isoxidized to yield a porous body. A fugitive phase may be included. Afugitive phase may include a material whose incorporation into a body(e.g., bound to other materials forming the body) may be followed by astep that decomposes the fugitive phase, leaving pores associated withthe shape, size, and/or distribution of the fugitive phase. A binder mayinclude a fugitive phase.

Repeated deposition of layers with concomitant delineation of portionsmay be used to build up a substrate. Built up substrates may be sinteredto remove a bonding polymer and form refractory bonds between particles.Substrates may be substantially comprised of fly ash. Substrates mayhave between 10 and 80% porosity.

An appropriately designed series of reactors may utilize the heat, massflow, and chemical species from a first reactor to improve theperformance of a second reactor connected to the first reactor.

A reactor may have an inlet and an outlet, and may include a substrateconfigured to react with (or provide for a reaction involving) a fluidpassing from the inlet to the outlet. A line from the inlet to theoutlet may describe a flow direction through the reactor. In some cases,the substrate includes a first end in fluid communication with the inletand a second end in fluid communication with the outlet. The substratemay include one or more channels to treat a fluid (e.g., gas or liquid)passing from the inlet to the outlet. In some aspects the first channelis in fluid communication with the inlet and the outlet. The firstchannel may be shaped to cause a fluid flowing through the first channelto take a direction that deviates from the flow direction by at least 5degrees, at least 10 degrees, at least 20 degrees, at least 30 degrees,or even at least 45 degrees. In some cases the deviation is less than 90degrees.

Some channels are shaped and/or include features to induce secondaryflows in the fluid flowing through the channel. A secondary flow (e.g.,an eddy, a vortex, and the like) may increase a deposition of a species(e.g., soot) on a wall of the channel. A secondary flow may increase aresidence time and/or contact time between the fluid and a wall of thechannel. A secondary flow may provide for improved chemical reactions.

Some channels may be helical. In some cases, substrates may be comprisedof helical channels, and an “interior” of the helix may be separatedfrom the “exterior” of the helix by the substrate walls. In some cases,the interior may be in fluid communication with an inlet and an exteriormay be in fluid communication with an outlet. The interior and exteriormay be in fluid communication via one or more channels.

Certain embodiments include filters. In some cases, a first channel maybe in fluid communication with an inlet to a reactor, and a secondchannel may be in fluid communication with an outlet of a reactor. Thefirst and second channels may be separated by a porous wall, such thatfluid passing from the first channel to the second channel may befiltered.

In certain embodiments, the first and second channels are helical. Thefirst channel may be in fluid communication with an exterior of thehelix, and the second channel may be in fluid communication with aninterior of the helix (or vice versa).

Some reactors include a first substrate having a first channelconfiguration and a second substrate having a second channelconfiguration. The first and second substrates may be arranged in series(with respect to fluid flow). The first and second substrates may bearranged in parallel (with respect to fluid flow). In some cases, thefirst and second substrates are helical and coaxial. In some cases, thefirst and second substrates have different numbers of channels, channelshapes, flow patterns (e.g., flow through or wall flow), catalysts,channel cross sectional area to volume ratios, channel porosity, andother factors. First and second substrates may include differentmaterials. A first substrate may be fabricated form SiC, and a secondsubstrate may be fabricated from cordierite. A substrate may includeash, such as fly ash, and may include cenospheres.

Some substrates may be configured for filtration of particulate material(e.g., from diesel engines). Some designs provide for flow fieldinstabilities that enhance the surface deposition of particulates onwalls of various channels. Certain substrates provide for “virgin”substrates having a first portion of higher permeability than a secondportion. Some substrates provide for a preferential flow and/orfiltration of particles in a region that heats up (e.g., from exhaustgas heat) more quickly than a second region.

Some substrates include channels having “channel plugs” that aredisposed within the substrate. In some cases, channel walls areconfigured to perform as channel plugs, which may increase a surfacearea of the “plugs” in some embodiments.

A substrate for use in a reactor having an inlet and an outlet, thesubstrate may include a a plurality of tubular first channels in fluidcommunication with the inlet, the tubular first channels includingchannel walls, at least a portion of the channel walls having a porositygreater than 20%; the plurality of tubular first channels connected toeach other by their channel walls. The substrate may include a pluralityof second channels in fluid communication with the outlet, the pluralityof second channels having shapes that correspond to the interstitialvolumes between the plurality of tubular first channels. The pluralityof tubular first channels may be square packed, trigonally packed,hexagonally packed, and/or randomly packed. In some cases, a randompacking may provide for a diversity cross sectional areas in theplurality of second channels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a reactor including a substrate, according to someembodiments.

FIG. 1B illustrates an exemplary flow-through substrate 112, accordingto some embodiments.

FIG. 1C illustrates an exemplary wall-flow filter substrate, accordingto some embodiments.

FIGS. 2A-C illustrates several features of some reactor substrates.

FIG. 3 illustrates an embodiment of a channel that includes flowmodifiers.

FIG. 4 illustrates views of a substrate according to some embodiments.

FIGS. 5A and 5B illustrate views of an “upstream” face (FIG. 5A) and“downstream” face (FIG. 5B) of a substrate according to someembodiments.

FIG. 6 illustrates a substrate according to some embodiments.

FIG. 7 illustrates a reactor according to certain embodiments.

FIG. 8 illustrates a substrate according to some embodiments.

FIG. 9 illustrates an exemplary array, according to some embodiments.

FIG. 10 illustrates an exemplary substrate, according to someembodiments.

FIG. 11 illustrates several substrate channel configurations, accordingto various embodiments.

FIGS. 12A-C illustrate different aspects of a substrate that may be usedfor (inter alia) filtration, according to some embodiments.

FIG. 13 illustrates various aspects of a channel, according to someembodiments.

FIGS. 14A-D illustrate subchannels incorporating inward/outward flow,according to some embodiments.

FIGS. 15A and B illustrate a substrate, according to some embodiments.

FIG. 16 illustrates an expanded view of a helical reactor, according tosome embodiments.

FIGS. 17A-C illustrate several channel designs, according to someembodiments.

FIG. 18 illustrates a system that may be used to fabricate bodies (e.g.,substrates), according to certain embodiments.

FIG. 19 illustrates fabrication method that may be used to fabricate abody comprised of different materials, according to some embodiments.

FIG. 20 illustrates a delivery of different materials (e.g., in the samelayer), according to some embodiments.

FIG. 21 illustrates a three channel substrate, according to someembodiments.

FIG. 22 illustrates a substrate combining two coaxial substrates,according to certain embodiments.

DETAILED DESCRIPTION OF THE INVENTION

Various aspects provide for reactors and the fabrication of reactors.Some reactors include surfaces that provide for heterogeneous reactionsinvolving a fluid (and/or components thereof). A fluid may be a gasand/or a liquid. A contaminant in the fluid (e.g., a dissolved orsuspended substance) may react in a reaction. Some reactors provide forindependent control of heat transfer (between the fluid, the reactor,and the environment) with respect to mass transfer (e.g., fluid flowthrough the reactor).

The design of a reactor may incorporate a combination of propertiesdescribing a fluid to be reacted. For example, a reactor comprising acatalytic converter may be designed according to an engine type (2stroke, 4 stroke, Atkinson cycle, Otto cycle, and the like), an amountof electrical hybridization (non-hybrid, mild hybrid, full hybrid), anexpected duty cycle (garbage truck, backup generator, string trimmer,tug boat, locomotive, and the like), a fuel source (bunker fuel, ULSD,gasoline, E85, biodiesel, premixed oil/gas solutions), and the like.Some reactors may be “disposable.”

FIG. 1A illustrates a reactor including a substrate, according to someembodiments. Reactor 100 may include a substrate 110 that interacts witha fluid flowing through the reactor. A reactor may have an inlet 130through which a fluid enters the reactor, and an outlet 140 from whichthe fluid exits the reactor. The combination of inlet and outlet (or afluid-flow direction) may describe “upstream” and “downstream” features.For example, a substrate may have an upstream face and a downstream faceaccording to the orientation of the substrate (e.g., with respect to thefluid flow).

A substrate is typically contained within a package, such as package120. A package may prevent uncontrolled mass transfer with theenvironment. Package 120 may be designed to improve heat flow into orout of the reactor (e.g., insulated at certain portions and/or heat finsat certain portions).

In many reactors, a fluid enters the inlet at a certain temperature witha certain composition and exits the reactor at another temperature andanother composition. Chemical reactions inside the reactor may beinfluenced (or even controlled) by heat transfer from the fluid to thesubstrate (and by extension between reactor 100 and the environment).

Surfaces of a substrate may be coated with a catalyst to modify areaction. A fluid may include a catalyst (e.g., dispersed in the fluid,such as a fuel-borne catalyst). A catalyst may be injected into areactor (e.g., upstream of the substrate). In some embodiments, acatalyst may be injected between the upstream and downstream regions ofa substrate.

FIG. 1B illustrates an exemplary flow-through substrate 112, accordingto some embodiments. A flow-through substrate may be a high surface area(e.g., highly porous) solid, and often includes a plurality of channelsthrough which a fluid passes.

FIG. 1C illustrates an exemplary wall-flow filter substrate, accordingto some embodiments. A wall-flow substrate may include a plurality ofupstream channels (plugged at a downstream end by downstream plugs 116)and a plurality of downstream channels (plugged at an upstream end byupstream plugs 118). A wall-flow substrate may filter a fluid byrequiring passage of the fluid through a wall separating an upstreamchannel from a downstream channel.

FIGS. 2A-C illustrates several features of some reactor substrates.FIGS. 2A-C illustrate views of an upstream face (FIG. 2A), side face(FIG. 2B), and downstream face (FIG. 2C). Demarcation as “upstream” and“downstream” is made for illustrative simplicity; a “downstream” facemay be disposed “upstream” in a given application. Substrate 200 (viewedin FIG. 2A) includes a plurality of upstream channels 210, defined bychannel walls 212. Downstream channels 220 may be created by pluggingareas between channels 210, for example using upstream plugs 230.Conversely, upstream channels may be plugged (in this example at thedownstream end) with downstream plugs 240 (FIG. 2C). As such, a fluidpassing into upstream channels 210 may pass through the channel wallsinto downstream channels 220. Substrate 200 includes “plugs” disposed atthe “ends” of the substrate. In some embodiments, channels may beplugged within the substrate (i.e., disposed from either end).

Certain embodiments include channels that may be characterized astubular. In some cases, tubes may be square packed (e.g., a tubecontacting four other tubes), hexagonally close packed (e.g., a tubetouching six other tubes), trigonally packed (e.g., a tube touchingthree other tubes). In some examples, a tube touches five other tubes.Packing of tubes may be modified to control (inter alia) the relativecross sectional area of upstream channels to downstream channels.

FIG. 2 also illustrates optional flow modifiers 250. A flow modifier maybe a structure that alters fluid flow through the substrate, through achannel, around a substrate, through a reactor, and the like. In theexample shown in FIG. 2, flow modifiers 250 include modifications tochannel wall shapes that may alter fluid flow (e.g., increaseturbulence) within the channels. Flow modifiers may be included withupstream channels, downstream channels, plugs, walls, and in otherregions. A flow modifier may induce deposition of a phase (e.g., soot)from a fluid being treated (e.g., in an eddy). A flow modifier maycreate a local region having reduced flow velocities, which may increasea contact time between the fluid and the substrate.

FIG. 3 illustrates an embodiment of a channel that includes flowmodifiers. Channel 310 includes wall 312 and flow modifiers 320. In thisexample, flow modifiers 320 are configured to modify a flow of fluidwithin channel 310 (e.g., flowing from inlet 330 to outlet 340). In thisexample, flow modifiers 320 are shaped to create eddies 360. Eddies 360may be used to increase a residence time and/or contact time between afluid and a wall. An optional catalyst 322 (e.g., associated with areaction requiring a “longer” contact time) may be preferentiallydeposited on and/or injected near a flow modifier (whose behavior mayincrease an average residence time).

Eddies 360 may enhance a deposition of entrained particulates (e.g., ina fluid in an upstream channel), as illustrated by deposit 370. In someembodiments, a flow-through filter may trap substantial quantities ofentrained particles by providing a large number of flow modifiers inupstream channels. Some embodiments may result in improved resistance toclogging by deposited particles. Flow modifiers may be used to (e.g., ina downstream channel) to slow the flow of fluid through the channel,which may result in increased transfer of heat from the fluid to thesubstrate prior to exiting the substrate. Certain embodiments include ahelical flow modifier, which may increase the transfer of heat from afluid to the substrate.

Various embodiments include channels designed to induce secondary flowsin a fluid (e.g., in addition to a primary flow describing flow of thefluid through or past a substrate). Secondary flows may be associatedwith instabilities in the flow field describing the fluid, and mayresult from features that induce a change in the flow path of the fluid.Curves and/or curvature in a channel may cause such instabilities. Flowmodifiers may cause such instabilities. In some cases, a feature and/orshape of a substrate may result in an induced instability and/or beassociated with a vortex or vortices. Certain substrates may induceTaylor vortex flow, Taylor-Couette flow, wavy vortex flow, spiral vortexflow, and/or other instabilities in a fluid. Some substrates may induceturbulent flow. Some embodiments includes channels having a changingcross sectional area with position in a fluid flow path (e.g., adecreasing cross sectional area, an increasing cross sectional area, a“neck” in the path, and the like).

FIG. 4 illustrates views of a substrate according to some embodiments.Substrate 400 may be disposed with respect to an inlet 410 and an outlet412. “Upstream” channels 420 may be separated from “downstream” channels430 by channel walls 440, which may be porous and provide for passage ofat least a portion of the fluid from upstream channels to downstreamchannels. Upstream channels 420 may receive a fluid from inlet 410, anda fluid may exit substrate 400 via downstream channels 430 to outlet412. Substrate 400 may include upstream plugs 430. In substrate 400, the“downstream plugs” may correspond to the shaped walls of the downstreamends of upstream channels 420. In this example, these ends are conical,although other shapes are possible.

In some embodiments, channel walls substantially form the upstreamand/or downstream plugs. In such cases, the surface area of the “plugs”may approach the surface area of the channels. For example, the circularcross sections at the upstream end of upstream channels 420 may be“flared” at the upstream end to form hexagonal cross sections, which mayincrease the total cross sectional area of upstream channels exposed toinlet 410. A transition from upstream to downstream need not bemonotonic (e.g., conical as shown in FIG. 4).

Channels may be separated by channel walls 440. In some embodiments, afluid enters upstream channels 410, passes through channel walls 440into downstream channels 430. Substrate 400 may be implemented as afilter.

Substrate 400 may be characterized by a length 470. In some embodiments,the cross sectional area of upstream and/or downstream channels may varyas a function of the length. In the example shown in FIG. 4, the crosssectional area of the upstream channels decreases in the “downstream”direction, and the cross sectional area of the downstream channelsincreases in the “downstream” direction. In other embodiments, crosssectional areas may vary in other ways (e.g., as with channels insubstrate 200 (FIG. 2)). In some embodiments, the variation of crosssectional area within a channel (e.g., an upstream channel) may bedesigned such that a substantial quantity of filtered material (e.g.,soot) is trapped a substantial distance from the outlet (e.g., 25% ofthe length “upstream” from the downstream end of the substrate, or even50%, or even 80%).

FIGS. 5A and 5B illustrate views of an “upstream” face (FIG. 5A) and“downstream” face (FIG. 5B) of a substrate according to someembodiments. Substrate 500 may include upstream channels 520 anddownstream channels 530. Porous channel walls may create a “transitionregion” (e.g., as illustrated in FIG. 4) between the channels, such thata fluid passes through substrate 500 by entering upstream channels 520,passing through channel walls into downstream channels 530, then exitingthe substrate.

FIG. 6 illustrates a substrate according to some embodiments. Substrate600 includes “upstream” channels 620, “downstream” channels 630, and maybe disposed with respect to inlet 410 and outlet 412 as previouslydescribed. Substrate 600 may include upstream plugs 632, and/or have anupstream face having a hexagonal channel shape (e.g., as in FIG. 5A).Substrate 600 may be designed with downstream plugs similar to plugs632. In this example, conical ends of upstream channels 620 may act asdownstream plugs. Substrate 600 may be characterized as having “plugs”disposed a first distance 672 from a downstream end of substrate 600 inlength 670. In some embodiments, particulate filtration may beconcentrated to volumes of the substrate substantially “upstream” fromthe downstream end. First distance 672 may be approximately 10% oflength 670, approximately 25% of length 670, approximately 50% of length670, and/or approximately 75% of length 670. First distance 672 mayapproach length 670 (e.g., be over 90% or even over 95% of length 670).

Substrate 600 also illustrates a transition region in cross sectionalarea of a channel. In this example, a transition region 680 indownstream channels 630 is illustrated. Downstream channels 630 mayinclude a first cross section 634 (in this case, approximately definedby the interstitial area between upstream channels 620). Downstreamchannels 630 may also include a second cross section 636 (in this case,larger cross sections toward the downstream end of substrate 600.Transition region 680 may generally describe a transition between firstcross sections 432 and second cross sections 434.

In some embodiments, transition region 680 may be located approximatelymidway between upstream and downstream faces of substrate 600. In someembodiments, transition region 680 may be located within 10% of length670 of either an upstream or downstream face of substrate 600. In someembodiments, transition region 680 may be located approximately 10%,20%, 30%, 40%, 50%, 70%, 80%, or 90% along length 670.

FIG. 7 illustrates a reactor according to certain embodiments. Reactor700 includes substrate 710 contained in a package 702. Substrate 710 hasan upstream channel 720 in fluid communication with inlet 722. Channel720 may be defined by a wall 730. In this example, downstream channel740 is in fluid communication with outlet 742, and may be defined bywall 730 and package 702. Wall 730 may be porous, and may filter a fluidpassing from upstream channel 720 through wall 730 into downstreamchannel 740.

Downstream plug 760 may form an “end” of upstream channel 720. Forconvenience, downstream plug 760 is referred to as “downstream” (e.g.,with respect to fluid flow), although downstream plug 760 may bedisposed at various points in reactor 700 (e.g., even at the upstreamface of the reactor, as shown in FIG. 7). In some embodiments, upstreamchannel 720 may be shaped such that downstream plug 760 is proximate toinlet 722. For the purposes of this specification, proximate is definedas “close enough that an effect of being close is manifest.”

In some embodiments, porosity, mean pore size, pore size distribution,channel cross section, wall thickness, tortuosity, and other factors mayvary as a function of length along a channel. For example, a region 770of wall 730 (close to inlet 722) may have a first pore sizedistribution, a region 780 of wall 730 (close to downstream plug 760)may have a second pore size distribution, and/or a region 790 (close tooutlet 742) may have a third pore size distribution.

In some cases, these factors may be used to control permeability througha wall as a function of position in the reactor. In some cases, controlof permeability may include control of the time dependence of thepermeability (e.g., as soot loading in the channel increases). A region780 may have a higher permeability than a region 790. A region 770 mayhave a higher permeability than a region 790.

In some filtration applications (e.g., as a particulate filter) wall 730may be fabricated such that particulate loading begins close todownstream plug 760. With downstream plug 760 designed to be close toinlet 722 (e.g., proximate to the upstream side of reactor 700), sootloading may occur preferentially in regions of reactor 700 that reachoxidation temperatures quickly (as compared to regions proximate tooutlet 742).

Certain components (e.g., substrates) may be fabricated from ceramics,such as SiC, Si3N4, cordierite, mullite, Al-titanates, and compositesthereof. Substrates may be fabricated from fly ash. Substrates may haveporosity ranging from 10-90%, including between 20 and 70%. Substratesmay have a surface area greater than 10 square inches/gram, and may begreater than 100 square inches/gram, or even greater than 1000 squareinches/gram. Some substrates (e.g., for filtration) may have a pore sizedistribution characterized by a median pore size and/or a mean pore sizebetween 1 and 100 microns, including between 4 and 80 microns, and/orbetween 10 and 50 microns. Some walls (e.g., between channels) may havea permeability greater than 0.5E-12/m^2, or even greater than 1E-12/m^2,including greater than 10E-12/m^2.

FIG. 8 illustrates a substrate according to some embodiments. Substrate800 may include an “inlet surface” 810 (which may face an inlet) and an“outlet surface” 820 (which may face an outlet). For clarity, inletsurface 810 is shown with darker/bolder lines and outlet surface 820 isshown with lighter/finer lines. Substrate 800 may be characterized by alength 830, which may be substantially longer than a diameter 832. Walls840 (e.g., porous walls) may separate (or define) inlet surface 810 fromoutlet surface 820.

In some embodiments, inlet surface 810 may be disposed facing inincoming fluid stream, outlet surface 820 may be disposed toward anoutlet, and a fluid may be treated by passing through walls 840. Channelexits 850 may facilitate a passage of treated fluid from interiorregions of substrate 800 to an outlet.

In some aspects, portions of substrate 800 may be shaped to alter fluidflow. For example, some upstream faces 860 of inlet surface 810. Someupstream surfaces 870 of inlet surface 810 may be concave. Downstream orside surfaces may also be shaped to modify fluid flow, and flowmodifiers may be included. Substrate 800 may include a channel plug 862,which may be located proximate to an “upstream” face associated withfluid flow. A channel plug may be porous, and may have a similar ordifferent porosity than other portions of the channel. A channel mayredirect fluid from from a direction toward the downstream face to adirection toward the upstream face, and/or a direction toward theupstream face to a direction toward the downstream face.

FIG. 9 illustrates an exemplary array, according to some embodiments.Substrate 900 may include an array (and/or other plurality) of similarlyshaped components (e.g., a plurality of substrates 800). The example ofFIG. 9 demarcates upstream (bold lines) and downstream (fine lines) asin FIG. 8.

FIG. 10 illustrates an exemplary substrate, according to someembodiments. Substrate 1000 includes channel 1010, which may approximatea helix having a radius 1020 (in this case, to a center of channel1010), a pitch 1030, and a length 1040. Openings 1050 and 1060 tochannel 1010 may be shaped and oriented as desired. For example,openings 1050 and/or 1060 may “face” outward with respect to the helix(facing in a direction other than parallel to the helical axis, e.g., asshown in FIG. 10). Openings 1050 and/or 1060 may face in the helicaldirection (e.g., “face” a fluid stream arriving at substrate 1000 from adirection substantially parallel to the helical axis).

A channel width 1012 and height 1014 may be chosen in combination withpitch 1030 to control a flow rate through the channel. For example, asmaller pitch may be used to reduce flow rate; a larger pitch mayincrease flow rate. A ratio of channel volume to channel surface areamay be controlled by the ratio of height 1014 to width 1012. In someembodiments, height 1014 and width 1012 are approximately equal. In someembodiments, width 1012 is larger than height 1014 (e.g., 2×, 5×, 10×,100×, or even 1000× larger). In some embodiments, height 1014 is largerthan width 1012. In some cases (e.g., for small pitches 1030), thelength of channel 1010 may be much greater than length 1040 of areactor, which may provide for increased contact time between a fluidbeing treated (passing from inlet opening 1050 to outlet opening 1060).An increased residence time may result in a greater amount of heat beingtransferred from a fluid to the reactor. In some cases, a catalyst 1012may be disposed on a surface of channel 1010. In some embodiments, afirst wall thickness 1080 between adjacent channels 1010 is differentthan a separate wall thickness 1082 associated with a wall betweenchannel 1010 and the “outer volume” of a reactor containing substrate1000. In some cases, wall thickness 1082 is substantially thicker (e.g.,twice, five times, or even ten times thicker) than wall thickness 1080.

FIG. 11 illustrates several substrate channel configurations, accordingto various embodiments. Substrates 1100, 1102, and 1104 may be helicalsubstrates (e.g., as described in FIG. 10), and illustrate (inter alia)different channel numbers and different pitches (although number ofchannels and pitch may be independently controlled). Substrate 1100 mayinclude a single channel 1110, and be defined by a first pitch 1120.Substrate 1102 may include two parallel channels 1110 and 1112, and maybe defined by a second pitch 1122. Substrate 1104 may include fourparallel channels 1110, 1112, 1114, and 1116, and may be defined by athird pitch 1124. In some embodiments, pitch may be controlledindependently of channel dimension (e.g., height 1014, FIG. 10) byvarying a number of parallel channels. The number of parallel channels,pitch of the channels, and surface area to volume ratio of the channelsmay be chosen according to various requirements of an application (e.g.,chemical reaction and/or residence time, heat transfer properties),typically in conjunction with the mechanical, thermal, and chemicalproperties of the material(s) used for the substrate. Openings tovarious channels may be shaped and oriented according as desired.

FIGS. 12A-C illustrate different aspects of a substrate that may be usedfor (inter alia) filtration, according to some embodiments. Substrate1200 may include a first channel 1210 and a second channel 1220,separated by a porous wall 1230. Channel 1210 may exposed to an inletand plugged with a downstream plug 1212, and channel 1220 may be exposedto an outlet and plugged with an upstream plug 1222. A fluid flowingfrom inlet to outlet may enter channel 1210, pass through wall 1230 intochannel 1220, and exit via the outlet to channel 1220. Substances (e.g.,particles 1240) may be filtered from the fluid by wall 1230. Substrate1200 may be characterized by a pitch 1250, a length 1260, a radius 1270and various dimensions of channels. Substrate 1200 is shown “expanded”in length 1260 in FIG. 12C. In some cases, a first channel may have alarger cross sectional area than a second channel. Channel ratios ofsurface area to volume, channel shapes, number of channels, pitches ofchannels, and the like may be chosen according to a desired application.

FIG. 13 illustrates various aspects of a channel, according to someembodiments. A substrate 1300 (e.g., a helical substrate) may includeone or more channels 1310. Channel 1310 may be divided into differentsubchannels 1320, 1322, 1324, 1326 by walls 1330. Subchannels may havesimilar or different cross sectional area and/or ratios of surface areato volume. Walls (e.g., walls 1330, 1332, and 1134) may be similar ordifferent thicknesses. In some cases, the cross sectional area of eachsubchannel may be combined with a radius of each subchannel (andoptionally pitch) to control the relative flow rates of fluids withinthe subchannels. In some cases, an “inner” channel may have a largercross sectional area than an “outer” channel. For example, channel 1326may have a width 1327, channel 1324 may have a width 1325, channel 1322may have a width 1323, and channel 1320 may have a width 1321.

In some embodiments, the expected fluid flow properties may be used tocalculate dimensions of various channels, and in some cases an “inner”channel having a tighter curvature may have a larger cross sectionalarea than an “outer” channel having a more gentle curvature. In someembodiments, an “outer” channel may have a pitch, curvature, and/ordimensions that result in preferential fluid flow through the outerchannel vs. an “inner” channel. In some embodiments, an “inner” channelmay have a pitch, curvature, and/or dimension that results inpreferential fluid flow through the “inner” channel vs. an “outer”channel. “Inner” and “outer” channels may have different pitches (e.g.,not be coplanar with respect to channel 1310 as shown in FIG. 11.

In some cases, a reactor and/or substrate design may include an expecteddeposition of particles (e.g., clogging), and an expected flow patternmay evolve as clogging increases. For example, substrate properties(e.g., channel shapes, sizes, and number) that result in an “outside-in”bias to a flow pattern. An unclogged substrate may cause fluid topreferentially flow through outer channels. As outer channels becomeclogged, fluid flow through inner channels may increase. In some cases,an unclogged substrate may cause fluid to preferentially flow throughinner channels. As the inner channels become clogged, fluid flow throughthe outer channels may increase.

FIGS. 14A-D illustrate subchannels incorporating inward/outward flow,according to some embodiments. A channel may be curved (e.g., into ahelix or ring) and may direct flow radially with respect to the curve.For example, channels 1400, 1402, 1404, and 1406 may include a pluralityof subchannels 1410 defined by walls 1420. In some cases, fluid flow maybe controlled to flow in a radial direction (e.g., inward toward theinside of the curve or outward toward the outside of the curve) inaddition to (or even instead of) flow in a longitudinal direction withrespect to a channel.

FIGS. 14A and 14B illustrate channels 1400 and 1402, and show twodesigns in which fluid may pass radially (from inside to outside,outside to inside, or in combinations). For example, FIG. 14Aillustrates radial flow from an exterior 1401 of a substrate having ahelical or ring shaped channel to an interior 1403 of substrate having ahelical or ring shaped channel, and FIG. 14B illustrates radial flowfrom interior 1403 to exterior 1401. In some embodiments, a firstchannel includes walls to cause a fluid to pass inward, and a secondchannel includes walls to cause a fluid to pass outward. Inward andoutward channels may be parallel. A reactor may include (in someexamples), a first helical channel having a structure as in channel 1400and a second helical channel having a structure as in channel 1402. Someembodiments include a combination of channels or substrates, arrangedsuch that a fluid enters a first channel, is treated (e.g., reacted) ina first manner and exits the first channel into a second channel. Thesecond channel may be proximate to the first, which may provide for heattransfer between the channels. In some cases, the fluid is treated in asecond manner in the second channel.

Some embodiments include a first channel and second channel separated bya porous wall. A fluid may be filtered upon passing from the first tosecond channels via the porous wall. The second channel may beconfigured to treat the filtered fluid. In some cases, a first channelmitigates a first contaminant (e.g., hydrocarbons), and a second channelmitigates another contaminant. In some cases, a first channel mitigatesNOx and a second channel mitigates particulate matter.

FIGS. 14C and 14D illustrate helical channels having plugs, which may beporous and/or combined with porous walls between channels (e.g., forfiltration). In FIG. 14C, channel 1404 may include an inlet (or outlet)1414 to the “outside” of the helix, and “inside” plugs 1424, which mayprevent passage (e.g., of particles) from the interior volume of thehelix to plugged channels. In FIG. 14D, channel 1406 may include aninlet (or outlet) 1416 and “outside” plugs 1426, which may preventpassage (e.g., of particles) from the outside of the helix to theplugged channels. Walls, tops, bottoms, plug, and other surfaces may befabricated from porous materials.

In an exemplary embodiment, a helical reactor incorporates a firstchannel as in channel 1404 adjacent to a second channel as in channel1406. Channels 1404 and 1406 may be separated by a porous wall. Fluidmay pass through inlet 1414 in fluid communication with an inlet of thereactor, through the walls into adjacent channels 1406, then exit thechannels 1406 via outlets 1416 to the interior of the helix. In such aconfiguration, “filtration” may occur primarily in a direction normal tothe page of FIGS. 14A-D, and may also occur at the inside and outsideplugs. In some embodiments, the interior of the helix may be in fluidcommunication with an outlet of the reactor. In some embodiments, theinterior of the helix may be in fluid communication with inlets ofadditional channels (e.g., channels configured for another type ofreaction). A distribution, shape, spacing and/or number of inlets and/oroutlets may vary as a function of position along a channel, position ina substrate, expected reaction, expected temperature profile, and thelike. For example, inlets 1414 may be preferentially concentrated at oneend of a substrate (e.g., an end facing an inlet and/or an end facing anoutlet).

FIGS. 15A and B illustrate a substrate, according to some embodiments.Substrate 1500 may include channels such as channel 1404 and channel1406 as described in the context of FIGS. 14C and D. FIG. 15 illustratesan exemplary reactor 1500 showing a plurality of inlets/outlets 1414 (onthe “outside” of the helix) and 1416 (on the “inside” of the helix). Thedescription “inlet” and “outlet” is for convenience; a substrate may beoriented “backwards” in some embodiments (e.g., the same configurationmay provide for “inward” flow or “outward” flow).

FIG. 16 illustrates an expanded view of a helical reactor, according tosome embodiments. Reactor 1600 may include a channel 1604 in fluidcommunication with an inlet (or alternately, an outlet) via inlets 1614,and a channel 1606 in fluid communication with an outlet (oralternately, an inlet) via outlets 1616. A fluid may be treated (e.g.,filtered) in passage from channel 1604 to channel 1606.

FIGS. 17A-C illustrate several channel designs, according to someembodiments. FIG. 17A illustrates a substrate with channels 1700disposed in a “checkerboard” pattern (as viewed “along” the channeldirection). FIG. 17B illustrates a substrate having a first channel 1710comprised of a first material and a second channel 1720 comprised of asecond material. FIG. 17B also illustrates different channels havingdifferent subchannel arrangements; in this example, second channel 1720includes a plurality of subchannels 1722, 1724, 1726, and the like. FIG.17C illustrates channels having concave and convex cross sections, andillustrates channels having different cross sectional areas and shapes.In this example, first channels 1730 have a first shape, and secondchannels 1740 have a second shape (which may be “complementary” to thefirst shape, or shaped according to the space “between” the firstchannels 1730). In some cases, a first wall 1750 between channels 1730and 1740 may be porous. In some cases, a second wall 1760 betweenadjacent channels 1760 may be a different material than a material offirst wall 1750. In some embodiments, channels 1730 may be in fluidcommunication with an outlet of a reactor and channels 1740 may be influid communication with an inlet to a reactor.

Two or more substrates may be connected to form a third substrate. Twoor more channels may be connected to form a combination of channels. Insome cases, reactors may be “integrated” by providing a first channelthat performs a first reaction and a second channel that performs asecond reaction. Heat and mass transfer calculations may be used todetermine a combination of geometrical and materials factors that mayresult in an integrated reactor using available heat and/or chemicalsfrom a first reactor to improve a reaction in a second reactor.

FIG. 21 illustrates a three channel substrate, according to someembodiments. Substrate 2100 may include helical channels 2010, 2020, and2030. In this example, an interior of the helical substrate 2100 may bein fluid communication with an inlet to a reactor containing thesubstrate. Inlets 2012 may allow for a fluid to pass from the inlet ofthe reactor to channels 2010. In this example, channels 2010 and 2020may be separated by a porous wall. A fluid passing through channels 2010may be filtered upon passing through the porous walls to channels 2020.The filtered fluid may exit channels 2020 via exterior outlets 2022.Channel 2030 may have exterior inlets in fluid communication withexterior outlets 2022. Filtered fluid may pass from outlets 2022 throughinlets 2032 into channels 2030. In this example, channels 2030 may havean outlet 2040 at an end of substrate 2100.

FIG. 22 illustrates a substrate combining two coaxial substrates,according to certain embodiments. Substrate 2200 may include firstsubstrate 2210 and second substrate 2220. Inlets and outlets associatedwith various channels (not shown) may be arranged as desired. In someembodiments, inlets to channels in substrate 2210 are disposed on the“outside” of substrate 2210, and may be in fluid communication with aninlet. Outlets associated with channels in substrate 2210 may bedisposed on the “inside” of substrate 2210, and may be in fluidcommunication with inlet channels associated with substrate 2220.Outlets from channels associated with substrate 2220 may be in fluidcommunication with the outlet of the reactor

In some cases, one of the two substrates may be in fluid communicationwith an inlet to a reactor containing substrate 2200, and anothersubstrate may be in fluid communication with an outlet of the reactor.An outlet to one of the substrates may be in fluid communication with aninlet of the other substrate.

Many reactors transfer heat to and from the environment. In some cases,heat transfer may proceed “radially” with respect to a helical substrate(e.g., a hot substrate loses heat to the environment in a radially“outward” direction. Some applications may benefit from “nesting” afirst substrate within a second substrate. In some cases, fluid firstflow through an outer first substrate, then flows through an innersecond substrate. In some cases, fluid first flows through an innerfirst substrate, then flows through an outer second substrate. Fluid mayflow through both substrates simultaneously. A first substrate may beconfigured to provide treatment under a first condition (e.g., a coldengine and/or stop/start operation) and a second substrate may beconfigured to provide treatment under a second condition (e.g., a hotengine and/or sustained, steady state operation).

FIG. 18 illustrates a system that may be used to fabricate bodies (e.g.,substrates), according to certain embodiments. System 1800 may include acontainer 1810 having a movable bottom 1820. A carrier 1830 may dispensea layer of precursor material 1840, which may include a ceramic, ametal, an ash, a cementitious material, a pozzolanic material, or othermaterials (typically particulate). A precursor material 1840 may includea binder and/or be intrinsically capable of being activated to causebonding among dispensed particles. Some precursor compositions (e.g.,class C fly ash) may be capable of forming cementitious bonds. Incertain cases, (e.g., pozzolanic materials, class F fly ash)complementary components (e.g., CaO, MgO, or other components) are addedto the dispensed material, such that the combination may formcementitious bonds when hydrated. A separate binder may also beincorporated into the precursor material, and may be dispensed bycarrier 1830 (e.g., as a mixture of binder and precursor materialpowders). A binder may also be dispensed as a separate layer (e.g.,sequential layers of binder and precursor material). A binder mayinclude polyethylene, a thermosetting resin, polycarbonate, a sugar, astarch, and the like. A binder may include an organic powder that reactswith an activator (e.g., a solvent) to cause the binder to glue variousother particles (e.g., ceramic particles) to each other. For example, asubstrate may be fabricated from cordierite powder, which may bedispensed as a mixture with powdered sugar. An activator (e.g., water)may be preferentially deposited on portions of a layer of the mixture,bonding the cordierite powder in the activated portion. A cementitiousprecursor material 1840 (or a pozzolanic material and a complementarymaterial such as CaO) may be activated by an aqueous activator.

A bonder 1840 (e.g., a laser for thermal bonding, an inkjet to apply abinder or activator, and the like) may be configured to bond at least aportion of the dispensed layer. Bonder 1840 may activate bonding amongparticles of precursor material 1840 and/or among a binder and precursormaterial 1840. Typically, bonding may create a solidified portion ofprecursor material 1840, shown as structure 1850. After bonding, bottom1820 may descend a small amount (e.g., microns to millimeters), carrier1830 may dispense another layer of precursor material 1840 (with or inaddition to additional binder), and bonder 1840 may bond an additionalportion of the new precursor material 1840, adding an additional layerto structure 1850. In some embodiments, structure 1850 may include asubstrate, channel, and the like. In some cases, a binder may beomitted. Companies such as 3D Systems (Rock Hill, S.C.), The Ex-OneCompany (Irwin, Pa.) and Z-Corporation (Burlington, Mass.) may providesome equipment for fabricating reactors. Various methods may be used tofabricate refractory (e.g., metallic, ceramic, and the like) havingporosity greater than 10%, greater than 20%, greater than 30%, greaterthan 40%, or even greater than 50%.

Printing methods (e.g., inkjet printing) may also be used to formreactors. For example, a bonder 1840 may provide for spatiallycontrolled deposition of a precursor material (e.g., as in an inkjetprinting head). Tape casting may be used for some embodiments.

FIG. 19 illustrates fabrication method that may be used to fabricate abody comprised of different materials, according to some embodiments.Inclusion of different materials in a body (e.g., a substrate) mayprovide for functional control of materials properties (e.g., differentregions of a reactor have different materials properties). For example,substrate 1900 may require fabrication from different materials 1910,1920, and 1930. Materials 1910, 1920, and 1930 might have differentparticle sizes, different particle size distributions, differentchemical compositions, include different binders, have differentcatalytic properties, have different permeability's, or have differencesand/or similarities in other factors.

Fabrication of substrate 1900 may include changing the precursormaterial delivered by carrier 1830 in system 1800. For example, a firstpart of substrate 1900 may be fabricating by delivering (e.g., layering)a first material 1910, a second part of substrate 1900 may be fabricatedby delivering (e.g., layering) a second material 1920, and a third partof substrate 1900 may be fabricated by delivering (e.g., layering) athird material 1930. Changing precursor material as a function of layermay provide for functionally graded properties in a “z” or “vertical”direction of a reactor (with respect to fabrication according to system1800). Some bodies may be fired. Firing may be used to remove a fugitivephase (e.g., via combustion of a carbonaceous fugitive phase). Firingmay also be used to aid the formation of interparticle bonds (e.g.,necks). Firing may also be used to change the composition, crystalstructure, particle size, grain size, and other aspects of a body.Select embodiments include selecting a first phase for forming a body,reacting the first phase to form a second phase during a formingoperation, and in some cases, forming a third phase during a firingoperation.

Firing times and temperature may generally depend upon a desiredapplication and body properties directed thereto. Generally,applications requiring more refractory bodies may require equivalentlyhigher firing temperatures. In some aspects, bodies are fired attemperatures between 400 and 800 Celsius. Bodies may be fired attemperatures between 800 and 1200 degrees Celsius. Some bodies may befired at temperatures between 1200 and 1800 degrees. Some bodiesincluding cordierite may be fired at temperatures between 1000 and 1600degrees. Some bodies including mullite may be fired at temperaturesbetween 1000 and 1950 degrees. Bodies requiring low temperature firingmay be enhanced by using ashes containing network modifiers such as K2Oand Na2O, or by adding these components. Bodies for use at temperaturesabove 500 Celsius may perform better by choosing an ash source havinglow (preferably negligible) amounts of less refractory materials such asK2O and Na2O. Certain compositions may form a liquid phase that firstenhances bonding, then reacts to form a solid phase (e.g., as inreactive sintering).

Certain aspects include firing in a coal fired, gas fired, microwaveenhanced, and/or electric furnace. In some cases, firing includescontrolled atmospheres, which may include oxidizing, reducing, forminggas, Nitrogen, and other atmospheres. Firing may be done in air. Somebodies do not require firing. Firing atmospheres may include theaddition of a gaseous component to prevent an undesired evolution of asubstance during firing (e.g., an overpressure of a gas).

FIG. 20 illustrates a delivery of different materials (e.g., in the samelayer), according to some embodiments. Such delivery may include usingcarrier 1830 and system 1800. Carrier 1830 may include differentmaterials 1910, 1920, and 1930, which may be delivered to fabricate areactor having functionally graded properties in an “x” and/or “y”direction of a reactor (with respect to fabrication according to system1800).

The above description is illustrative and not restrictive. Manyvariations of the invention will become apparent to those of skill inthe art upon review of this disclosure. The scope of the inventionshould, therefore, be determined not with reference to the abovedescription, but instead should be determined with reference to theappended claims along with their full scope of equivalents.

What is claimed is:
 1. A substrate for use in a reactor having an inletand an outlet, a line from the inlet to the outlet defining a flowdirection, the substrate comprising: a first end configured to be influid communication with the inlet; a second end configured to be influid communication with the outlet; and a first channel having a porouswall having a porosity between 20% and 70% and open to at least one ofthe inlet and the outlet, the first channel having a shape that causes afluid flowing through the first channel to take a second direction thatdeviates from the flow direction by at least 5 degrees, wherein the flowdirection and the second direction define a plane, and at least aportion of the first channel has a shape that causes the fluid flowingthrough the portion to follow a third direction that is not coplanarwith the plane.
 2. The substrate of claim 1, wherein a primary flowfield describes a predominant flow of the fluid through the firstchannel, and the first channel includes one or more flow modifiersshaped to induce a secondary flow field in the fluid.
 3. The substrateof claim 1, wherein the second direction deviates from the flowdirection by an amount that is between 5 degrees and 180 degrees.
 4. Thesubstrate of claim 1, wherein the first channel includes a plurality ofsubchannels.
 5. The substrate of claim 1, wherein at least a portion ofthe first channel has a channel flow direction associated with a fluidflowing through the portion of the first channel, and the portionincludes at least one subchannel causes the flowing fluid to follow asecond direction different than the flow direction.
 6. The substrate ofclaim 1, wherein the porous wall has median pore size between 1 and 100microns.
 7. The substrate of claim 1, wherein the first channel is opento both the inlet and the outlet.
 8. The substrate of claim 1, furthercomprising a second channel through the substrate, wherein the firstchannel is open to one of the inlet and the outlet, the second channelis open to the other of the inlet and the outlet, and the porous wallseparates the inlet from the outlet.
 9. The substrate of claim 8,wherein the first channel is open to one of the inlet and the outlet,and the second channel is open to another of the inlet and the outlet.10. The substrate of claim 1, wherein the porous wall is permeable. 11.A substrate for use in a reactor having an inlet and an outlet, a linefrom the inlet to the outlet defining a flow direction, the substratecomprising: a first end configured to be in fluid communication with theinlet; a second end configured to be in fluid communication with theoutlet; and a first channel having a porous wall having a porositybetween 20% and 70% and open to at least one of the inlet and theoutlet, the first channel having a shape that causes a fluid flowingthrough the first channel to take a second direction that deviates fromthe flow direction by at least 5 degrees, wherein the first channelincludes a first section and a second section: the first section causingthe fluid flowing through the first section to flow in a direction thatis within 5 degrees of opposite the flow direction, and the secondsection causing the fluid flowing through the second section to flow ina direction that is within 5 degrees of the flow direction.
 12. Thesubstrate of claim 11, wherein a primary flow field describes apredominant flow of the fluid through the first channel, and the firstchannel includes one or more flow modifiers shaped to induce a secondaryflow field in the fluid.
 13. The substrate of claim 11, wherein thefirst channel includes a plurality of subchannels.
 14. The substrate ofclaim 11, wherein at least a portion of the first channel has a channelflow direction associated with a fluid flowing through the portion ofthe first channel, and the portion includes at least one subchannel thatcauses the flowing fluid to follow a second direction different than thechannel flow direction.
 15. The substrate of claim 11, wherein theporous wall has a median pore size between 1 and 100 microns.
 16. Thesubstrate of claim 11; wherein the porous wall is permeable.
 17. Thesubstrate of claim 11, wherein the first channel is open to both theinlet and the outlet.
 18. The substrate of claim 11, further comprisinga second channel through the substrate, wherein the first channel isopen to one of the inlet and the outlet, the second channel is open tothe other of the inlet and the outlet, and the porous wall separates theinlet from the outlet.
 19. A substrate for use in a reactor having aninlet and an outlet, a line from the inlet to the outlet defining a flowdirection, the substrate comprising: a first end configured to be influid communication with the inlet; a second end configured to be influid communication with the outlet; and a first channel having a porouswall having a porosity between 20% and 70% and open to at least one ofthe inlet and the outlet, the first channel having a shape that causes afluid flowing through the first channel to take a second direction thatdeviates from the flow direction by at least 5 degrees, wherein at leasta portion of the first channel forms at least one of a helix and a ring.20. The substrate of claim 19, wherein an interior of the helix or ringand an exterior of the helix or ring are in fluid communication via thefirst channel.
 21. The substrate of claim 19, wherein a primary flowfield describes a predominant flow of the fluid through the firstchannel, and the first channel includes one or more flow modifiersshaped to induce a secondary flow field in the fluid.
 22. The substrateof claim 19, wherein the first channel includes a plurality ofsubchannels.
 23. The substrate of claim 19, wherein at least a portionof the first channel has a channel flow direction associated with afluid flowing through the portion of the first channel, and the portionincludes at least one subchannel that causes the flowing fluid to followa second direction different than the channel flow direction.
 24. Thesubstrate or claim 19, wherein the porous wall has a median pore sizebetween 1 and 100 microns.
 25. The substrate of claim 19, wherein theporous wall is permeable.
 26. The substrate of claim 19; wherein thefirst channel is open to both the inlet and the outlet.
 27. Thesubstrate of claim 19, further comprising a second channel through thesubstrate, wherein the first channel is open to one of the inlet and theoutlet, the second channel is open to the other of the inlet and theoutlet, and the porous wall separates the inlet from the outlet.